No Voltage To Coil

""The only change was the ECU & when you confirmed the ground the prob went away""

After replacing the first coil with a known good second coil, then I grabbed a second good ECU and laid it on the valve cover. Once I added a ground wire to the second ECU, that was when the voltage came back at the coil wire. Then I just moved the harness off of the second ECU back to the first ECU (which I never removed) and then I got spark from it again. This is why it does not make sense, unless I have an issue in the harness.

Would the pickup gap cause this? The last time that I checked it, I had it set at .008".
Thanks

air gap could cause this but i would like to think it would be all the time. i think plugging and unplugging the harness 'pushed' the ECU into making a ground. in looking at the pic, it appears your ECU is mounted on a bracket and the bracket is mounted to the firewall? if this is true clean up all the mounts and maybe put some of that grease between all the areas. i used to put stainless washers behind the box and scraped the firewall bare. now i use MSD so i don't have that problem anymore.

I added a ground wire to the ECU body mounting bolt and checked the one on the mounting bracket. I also removed the ECU connector and added dielectric grease and put it back on a little more snug than the last time.
Don told me to make sure of the reluctor gap so I pulled my dist and the gap was about .006". So I cleaned the connectors and restarted the car twice with no issues.
I did not see anything obvious so I will keep an eye on the issue.

Thanks to everyone for the replies.

""being paranoid about a potential breakdown is no fun & takes the fun out of it""

That is exactly what I was thinking Saturday when I finaly got it restarted but I did not know why. I was gun-shy to drive it until I had the time to investigate it. I hate that feeling.

Thanks Robert.

IT DID IT AGAIN!!

I drove the car twice this afternoon with no starting problems. I tried starting it again for the third drive and no start. So I pulled the coil wire and confirmed no spark to coil. This time the engine only sat for 10 minutes or so and then a no start. So I pulled the harness at the ECU and just put it back on and no spark at coil. I ran out of time but I will swap ECU's later to see if that it the issue.
This is exaclty what happened last time. It seems that after an hour or so of driving, something goes and it wont give a spark.

Thanks for listening (or reading )


Update:
I tried two hours later to check for spark at the coil and nothing. I was thinking that maybe something was getting hot. Then I swapped out the ECU and had major spark. Then I swapped back to the first ECU and found very minimal spark from the coil at start. It appears that the first ECU does not want to fire at startup.

Put the new ECU back on & if that takes care of it for several days w no probs give the 1st one a good toss against the wall (it'll make you feel better)

Have you checked the air gap on the reluctor & pick up coil... A weak pick up coil can also cause the issue...

Two weeks ago when this happened, I was directed to check the pickup gap. The gap was apx .006". I did not recheck it this time because swapping from ECU #1 to ECU #2 gave me spark again. Then swapping back from ECU #2 to ECU #1 gave me no spark again.
I am contacting the manufacturer today to try and get the #1 ECU replaced.
Note: #1 ECU is only about 4 months old. #2 ECU is about 4years old and it appears to be still going strong.

I would throw #1 ECU against the wall but I want my warranty.

Thanks

It has a 2 year return policy and I have only had it for 4 months. I should know later on today.

Reluctor gap should be .008.

The problem I see is you are swapping parts and did not do a systems check. You needed to verify your votages and ground connections to see where the drop is. That way you can fix it and move on. Swapping parts does not fix the problem.

I confirmed battery voltage as soon as the problem showed up. I have two grounds, one at the base of the ECU (mounting bolt) and the second at the base of the mounting bracket for the ECU (mounting bolt). I assumed that swapping a known good second ECU and finding spark then re-testing the first ECU and finding no spark again was a good test for a bad part.

Note: The second ECU was not mounted. I just moved the harness from the first ECU and plugged it into the second known good ECU. Then I used a wire with two alligator clips to ground the body to the ground wire on the first ECU. This setup showed spark at the coil wire.

What do you suggest I try?


Thanks for the reply.

You have to verify voltage to the ecu during cranking. If no voltage than either bad connections at ballast or bad ignition switch.

I will check that out.
If cranking voltage goes thru the brown wire to the positive of the coil, then which pin number at the ECU do I need to check voltage at while cranking?

Thanks

I've had problems with the ECU's going bad in my truck about every 2 years or so. They don't visibly show any problems but no spark. I had one go bad in Lowes parking lot with no warning and left me stranded. Shortly before that it would get heat soaked when parked and would create a no-start situation. Leave it sit for 3-4 hours and it would fire right up!

I've had to mess with making sure that they're grounded to the inner fender. Lose that ground and you'll get a no spark situation as well. My truck sits out in all kinds of weather so occasionally I'll rough up the back of the ecu and the fender mount locations with some sandpaper.

I've threatened more than once to put an MSD on the darned thing (since all my Mopar cars get them) and eliminate the ECU and ballast resistor but it's just a junky old truck.

Then again I HATE something that isn't stone reliable.

Every body here has a good point.
A ground to the Ignition Control Module is essential for the Module to function. A dedicated ground wire ensures a reliable ground source.
Air gap specs vary by year. I use 0.006 with a brass feeler gauge. As long as the reluctor does not strike the pickup, and you can feel the pull, it is within functional range. But the pick up does not usually fail and come back to life after cooling. The status of the pick up coil has no effect on power TO the coil, but is essential for spark test and system function.
The ignition coil will usually provide poor performance when it is failing. A no-spark condition when hot is a classic coil failure, but the coil will often cut out while operating.
The Ignition Control Module will also provide a no-spark when hot condition. However it will usually run fine and fail after operator shuts off and not just cut out on you. But this is not 100% reliable. That's why we use test equipment and follow standard diagnostic procedure.
I am confused on your testing. Your subject is "No Voltage To Coil", yet your test response is always listed as spark or no spark.
Voltage test at coil with your digital voltmeter should read within 1 volt of battery voltage with key on, and engine not running. + Lead on coil + and - Lead on a good ground. This is not a computer car, so if you do not have a digital Volt Ohm Meter, you can use a test light if you can recognize differing battery voltages with it. The Module and the Coil share the same Power feed. If you don't get power to the + on the coil with key on, turn key off, disconnect plug on Module, turn key on , and check for power on the back side of the wiring connector. If you get power in one place and not the other, check wiring. If your voltage at coil and the Module are within range, you don't need to test ignition switch or firewall connection, but cleaning and dielectric grease is excellent for preventative maintenance.
Testing for spark: In one instance you wrote " no spark to coil." Uh Oh! I am looking for spark coming FROM the coil's high tension wire (in the middle of the coil) to a spark tester. The spark tester takes the place of the distributor cap for testing. You can buy a spark tester from the tool truck, or parts store or make one from a known good spark plug, hose clamped on to an alligator clip. KEEP AWAY from open carburetor! I have been known to clip a jumper wire on my spark tester to ground.
Note: Always turn key off before making or breaking connections as the system WILL spark due to power or pickup connection change.
I do believe you replaced the defective part and fixed the problem through trial and error substitution/replacement procedure.

""I am confused on your testing. Your subject is "No Voltage To Coil", yet your test response is always listed as spark or no spark""

Sorry, I should have wrote, no spark to distributor. Both occasions in this thread should have meant no spark to distributor.
I will double check the voltage to the coil and the voltage to the ECU tonight just to make sure they are both seeing voltage during CRANK and RUN modes.
- Which pin number on the above picture should I be looking at for voltage at the ECU during crank and run?


Thank you.

""When checking voltage with key on and cranking you check it at the + terminal at coil""

Is this because the ECU sends the signal to the coil?

I hope to find time tonight to check these voltages.
Thanks again.

The coil (positive pri terminal) and the ECU both need fire in start (ballast bypass ign2) and in run (thru ballast ign1) for those 2 components to function. The dist pickup triggers the ECU (by generating a small A/C voltage) which makes the ECU in turn trigger the coil (by making an "open" in the wire to the coil neg pri terminal)

I took voltage readings at the "+" side of the coil with both ECU's. (A) is the first ECU that was not showing any spark at the cap and (B) is the known good ECU. ECU (A) is now showing a VERY minute spark and ECU (B) shows a massive spark that shoots down the length of my screw driver.
ECU# Run @ Coil Crank @ Coil
A 11.2v 10.1v (non ballast ECU)
B 8.0v 8.0v (ballast ECU)

Even though ECU (A) showed 10.1v at the "+" side of the coil, the spark was very light @ crank. Even though ECU (B) showed 8.0v at the "+" side of the coil @ crank, the spark was massive.
I now have ECU (B) hooked up and I have no doubt that due to the strength of the spark that it would have no problem starting.
Does this still indicate that ECU (A) is faulty?

Note: I also checked the ground at the mounting bolts of the ECU and the mounting bolts of the ECU mount bracket and they all four showed battery voltage when the positive side of the lead was on the battery.

Note: I have read where there might be a GM HEI unit inside of this ECU. If this is true, I have also read that it takes at least 11.0v to get one to supply enough power for the START mode. I show only 10.1v at the coil during cranking. But this doesn't make sense. This no start issue started on Sunday morning when the car sat for four days and it started just fine. Then after the second half hour drive the car sat for 10-15 minutes and then the no start issue was found. This was the exact same situation that happened about two weeks ago but then the no start issue just went away.

Thanks

You only have a certain amt of (electrical) energy to work with. With ECU (B) making the coil secondary kick out a massive spark you would naturally have much lower readings at the coil pri cause that circuits' energy is being consumed to power up the secondary just like when a toilet is flushed a person in the shower can (& has) gotten scalded from the lower pressure (voltage) as there's only so much flow (amperage) available. ECU (A) must not be cutting the coil neg pri circuit off clean to make the secondary collapse good like ECU (B) is but I dont know electronics so I'm speculating

Update:
I talked to FBO and I will be sending the ECU back for a rebuild. They have found that some of the newer distributor magnetic pickups on the market have a lower minimum voltage and his ECU can not pickup on this low voltage. So he is working on a fix for the ECU's that consist of a amplifyer to raise this voltage and he is also adding a rev limiter. These items will be on his newer ECU's but he is rebuilding the current ECU's that are having this no start issue with these parts free of charge, except for the initial shipping of the unit back to FBO. I explained my issues (stated in this thread) and he said that about 10% of his customers are seeing the same issue. He told me that the older magnetic pick-ups are putting out enough voltage but the new aftermarket pick-ups (which I just replaced) do not have the voltage output for his system to read.

Sounds good and you'll be up & running with his ECU & (I'm assuming) matching killer coil plus ECU(B) for a backup. I had one of his black coils and it started leaking right off the bat out of the tower so I shut it down & swapped it out & sat on it for over a year & I called Don & explained that it only had 5 min run time & that I had gotten chronically ill & that I had done no work in that length of time which doesn't sound believeable at all but it was what happened to me and he exchanged it . I'm wondering if there is an ohm diff to tell if it'll fire his ECU. Luckily all of my dizzys are old OE stuff

ECU (A) is his new ECU and ECU (B) is his old ECU and my backup "if" I run a ballast.
I will be getting mine rebuilt into the new ECU that will be coming out in the near future.

What are the specifications for voltage output of the pick up coil?

Chrysler Electronic Ignition
No Spark Condition Testing Procedure


1 Measure Battery Voltage at the Battery while Cranking. Minimum requirement is 9.6 V DC.
2 Remove Coil wire from center of Distributor Cap, connect a spark tester and it clip to a good ground. Connect one end of a jumper wire to the Coil -, turn Key ON. Drag or tap other end of jumper wire on a good ground. A small spark should be observed.
3 If no spark is observed, turn Key OFF, disconnect wire plug from Ignition Control Module (ICM) aka ECU, turn Key ON, drag or tap jumper wire to good ground. If a spark is observed, REPLACE THE ICM.
4 If no spark is observed, check voltage at Coil +. It should be within 1 volt of battery voltage. If yes, check Coil -. It should be within 1 volt of battery voltage. If no voltage is present, check wiring.
5 If voltage is present at the Coil -, but no spark occurs when arcing the Col – jumper wire to ground, REPLACE the COIL.
6 With wire harness plug removed from ICM, turn Key ON. Check for voltage in cavity 2. It should be within 1 volt of battery voltage. If no voltage is present but is at Coil -, replace wiring, and repair fault.
7 With Key ON, check for voltage in cavity 1. It should be within 1 volt of battery voltage. If not, check wiring and repair fault. Repeat test while cranking. Voltage should be at least 9.6 V.
8 With Key OFF, check resistance between cavity 4 and cavity 5. It should read 150 to 900 Ohms. If not, disconnect wire from Pick up coil. Check resistance. If out of range, REPLACE the PICK UP COIL. If your two measurements are different, check wiring and repair fault.
9 Check resistance with each of the wires on the Pick up coil to ground. If not open, REPLACE the PICK UP COIL.
10 Check pin 5 of the ICM (not the harness) for ground. If no ground, run dedicated ground wire to body of ICM.
11 If all tests are good, and still no spark, REPLACE the ICM.

Electronic Ignition did not come factory on 1970 Challenger. The wiring diagram you provided shows a ballast resistor, yet you said in your first post "Non-ballast ignition".
Are you using the wire on pin 3 for anything? Are your Ign 1 and Ign 2 wires from Key tied together feeding pin 1 and Coil +?
This is the diagram I use for a Non-ballast Ignition.

I can't give you details because I am not qualified, but I believe that he said the current magnetic pickup coils are to be built for .02-.05v somthing or other. The old style pickup coils were built closer to the .05v range and all of the newer coils are built closer to the .02v range due to being cheaper to build. His prototype testing was done on a .05v unit and when the .02v units hit the market is when he started seeing more issues with the no start. Then he worked with his vendors to come up with the added amplifyer solution.
Don at FBO can give you all the details. I am just trying to give some information on what happened on my issue. I just appreciate Don upgrading my existing equipment to help me fix the problem.

I attached a schematic that I have referenced in the past and it was not intended for a 70 application like I have. It was only intended for a quick reference.
Thank you very much for the detailed write up on the no spark troubleshooting and your schematic is a good one!!

You are quite welcome. I have been looking for that spec for a while. Thank you.

I left out one test, checking Coil - for power while cranking. You need an assistant, some body like the neighbor or in-law who never returns tools, or the EX. Make SURE you put your spark tester on the wrong end of the coil wire for this test. Jack up the car and lower the hood to get the geometry right. ...

Can any body identify this test equipment?

I'm thinking that a healthy pickup will generate ~1 volt AC on your VOM while cranking. Seperate the 2 wire offset pickup connector & connect to the pickup side & have your neighbor crank it (dont let the male terminal of the other half of the connector touch a ground while it is dangling). EDIT above pic, portable ECU/coil/ballast combo to diagnose the system or hot wire it for a test drive.